Cannot sign into account

Punkcakes follow what WPAK says. If you can sign into xbox.com with your correct gamertag it sounds like you may just have a corrupted profile. The only thing I would add to WPAK suggestions would be with #3 clearing the cashe I would check the hard drive
for other corrupted content. If you have a HDD (Hard Drive) and a MU (Memory Unit) go into them, then go into each folder "Games & Apps, Profiles, Demos" (demos are notorious for corruption), all the way down to system items. Anything with an exclamation point
indicates it's a corrupted file and needs to be deleted. Even if your profile doesn't have an exclamation point it may still be corrupted and needs to be deleted (remember profile only!).

But if you follow the instructions that WPAK gives you should be able to get it again, let us know if it works or if it doesn't, any error codes you get, etc.

Please try to power cycle your console and try again.

Follow these steps to power cycle your console:

1. Turn off the Xbox One console by pressing the Xbox button on the front of the console for about 10 seconds until it shuts down completely.
2. Unplug the console's power cable. Wait 10 seconds.
   Important Be sure to wait 10 seconds. This step resets the power supply.
   
3. Plug the console power cable back in.
4. Press the Xbox button on your console to turn on the Xbox One.

Hi there,

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try the following steps.

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1. Check
account.live.com/.../manage to see if at least two security proofs are setup and verified. A Phone number and alternate email address would be best

2. Delete your profile from the console, be sure to delete only the profile, to do so check this link:

support.xbox.com/.../profile-move-delete

3. Clear the console cache, see this link for the how to:
support.xbox.com/.../clear-system-cache

4. Turn the console off.

5. Turn the console on.

6. Clear the console cache one more time

7. Redownload your profile.(See the same link as 2.) you might have to enter the security verification afterwards and all should be fine again.

I had this same problem, i restarted the console and the logged onto my internet again (even if it was already connected then everything started working.

Did you troubleshoot with Xbox customer service? If I may suggest, to just reset password then try again?